Antiphospholipid antibodies, both anticardiolipin and lupus anticoagulant, are common in SLE. We asked, in a prospective cohort, whether these antibodies are predictive of atherosclerosis and/or coronary artery disease. Three hundred eighty patients, 92% female, 49% Caucasian, 51% African-American, mean age 46.4+/-12.3 years are followed quarterly, with assessment of both anticardiolipin and lupus anticoagulant (dRVVT). These patients underwent both helical CT and carotid duplex. Both the lupus anticoagulant and anticardiolipin are predictive of later venous or arterial thrombosis. Twenty years after diagnosis, SLE patients with the lupus anticoagulant (LA) have a 50% chance of a venous thrombotic event. Myocardial infarction occurs significantly more often in those with LA 22% vs. 9%, p=0.04. Neither anticardiolipin nor LA are associated with carotid IMT, carotid plaque, nor coronary calcium by helical CT. In aCL positive patients carotid IMT was 0.57+/-0.01 vs. 0.58+/-0.01 in aCL negative patients (p=NS); carotid plaque 0.47+/-0.13 vs. 0.32+/-0.10 (p=NS); and coronary calcium 65.4+/-37.4 vs. 65.4+/-30.2 (p=NS). In LA positive patients, carotid IMT was 0.59+/-0.03 vs. 0.59+/-0.02 in LA negative patients (p=NS); carotid plaque 0.07+/-0.02 (SE) vs. 0.80+/-0.02 (SE) (p=0.06); and coronary calcium 28.1+/-3.7 (SE) vs. 85.7+/-2.6 (SE) (p=NS). Antiphospholipid antibodies are not associated with subclinical atherosclerosis (carotid IMR, carotid plaque, helical CT coronary calcium), but are associated with actual thrombotic sequelae (myocardial infarction).